The present invention relates to a method of suppressing noise having an alternating voltage component in a load supplied with a direct voltage signal by way of a control loop including a final controller connected to the load, and to an arrangement for implementing the method.
In many cases, loads are supplied with direct voltage by way of a final controller, for example the final controller of a series controller as disclosed in German laid-open Patent Application No. DE-OS 2,822,897, and "Funk Technik" [Radio Technology] Vol. 37, No. 9 (1982), pp. 385-388. Voltage fluctuations in the supply source, fluctuations in the load and noise signals, for example mains hum, can be eliminated with the use of such a final controller.
The publication "Electronics", Oct. 6, 1982, pages 110-111, discloses the connection of a controlled choke subsequent to a switch controller in order to suppress alternating voltage (ripple) noise signals. By way of a capacitive sensor, the circuit disclosed there detects the load voltage (direct and alternating components) and feeds it to a differential amplifier. The alternating component appearing at the output of the differential amplifier is added to the choke in phase opposition to the alternating component of the load voltage. It is difficult to suppress low-frequency ripple with such an arrangement. Fast changes in current at the output, as they occur, for example, in TDMA satellite systems, cause considerable overshooting.
The publication "Revue de Physique Appliquee", Vol. 9, May, 1974, pages 533-537, discloses, for a high voltage direct current supply system, the connection of a differential amplifier by way of a capacitive voltage divider with a load terminal in order to reduce noise voltage and to feed the output signal of the differential amplifier, in phase opposition, to a control input of the high voltage generator.